From past, various fastening devices have been developed. Patent Literature 1 discloses, in its abstract, that a hook part (23) is simply and firmly connected to a connection body (11) attached to a belt. Additionally seeing FIGS. 2 and 3 of the same document, an inside (16) of the connection body (11) is shaped to be a semispherical cavity and a coupling recess (15) having an insertion hole (19) is provided in a base portion (18) thereof. A hook part (12) is provided with a spherical coupling portion (21), a hook part (23) having a locking portion (22) at a distal end extending from the coupling portion (21) and an auxiliary latch (24) parallel to the hook part (23). As shown in FIG. 2, when the hook part (23) of the hook part (12) is inserted into the coupling recess (15) of the connection body (11), the coupling portion (21) of the hook part (12) engages with a semispherical cavity (16) of the connection body (11) and rotatably couples therewith.
Patent Literature 2 discloses, in its FIGS. 1 and 2, a structure in which a guide piece (13), a locking piece (14) with a lug (16) and a bridge (15) are provided in a coupling portion (10) of a loop clutch body (2) used for coupling with a support body (1). The document describes that this structure allows the loop clutch to be assembled to the support body (1) by simple manipulation and can reduce backlash and keep smooth rotation.